Write only one line and update the file

[gnusmas]

Hello there.

I want that the actual altitude of my aircraft is written to a line in a txt file, and the file should be permanently updated. So i've changed the "record to csv.lua" file into like this

 

-- "Record to CSV" example data logging LUA plug-in, by Pete Dowson, September 2008

-- Open an exisitng "FSrecord.csv" file to append to, or create it if it doesn't exist
-- It will go into the Modules folder because I've not included a full path (like "C:\....")
-- By using "assert" you get an error message if this fails

f = assert(io.open("alt.txt","w"))


--  note the elapsed mSecs count now so can provide relative mSec timing column
time0 = ipc.elapsedtime()

-- Loop until our Flag 0 is set (by assigned FSUIPC control)
while not ipc.testflag(0) do

-- Set the timestamp for this loop
time = ipc.elapsedtime() - time0

-- Read all the data we want from FSUIPC
lat, lon, alt, pitch, bank, hdgT = ipc.readStruct(0x0560,"3DD", "2SD", "1UD")

-- now convert them all from FS units into those we normally recognise

alt = alt * 3.28084 / (65536 * 65536)


-- but only log this time IF we aren't in an FS menu, or loading scenery
-- (check the "ready-to-fly" flag word at 3364)
-- and provided we are not paused (flagged at 0264)


if (ipc.readUW(0x3364) == 0) and (ipc.readUW(0x0264) == 0) then

   -- write a CSV line to the open file
   f:write(string.format("%.1f\n",
	alt))
end

-- 20 times per second, roughly (allow 2 mSecs overhead)
ipc.sleep(48)

end

-- tidy up at end ...
f:write("\n")
f:close()

-- end of example program

This works perfectly fine...

But now the output in the "alt.txt" is for example:

21.8
21.8
21.8
21.8
21.8
21.8
21.8
21.8
21.8
21.8
21.8
21.8
21.8

i want just one line that should be updated, and not a ton of new lines. is there a way to manage this? and where should i change the script to let it do this?

 

thanks :)

[Pete Dowson]

10 minutes ago, gnusmas said:

i want just one line that should be updated, and not a ton of new lines. is there a way to manage this? and where should i change the script to let it do this?

You'd need to re-create the file every time, doing the open, write and close all together.

Pete